观察下列算式：

1+3=4=2²

1+3+5=9=3²

1+3+5+7=16=4²

1+3+5+7+9=25=5²

你能得出怎样的结论？

The sign reading "No Photos" means that no one ____ take any photos in the Palace Museum.

A．need

B．may

C．must

D．shall